Amount Of Sulfonic Acid Groups Research Articles

Long-term performance of polyetheretherketone-based polymer electrolyte membrane in fuel cells at 95 °C

A poly(styrenesulfonic acid)-grafted polyetheretherketone (ssPEEK) polymer electrolyte membrane was developed by radiation grafting of ethyl styrenesulfonate (ETSS) onto PEEK film and subsequent hydrolysis. The long-term durability of the ssPEEK electrolyte membrane was tested in a fuel cell at 95 °C, during which it exhibited a lifetime of more than 1000 h and a slow voltage degradation of 18 μV h−1 at a current density of 0.3 A cm−2. After durability test, the catalyst layers were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM); the polymer electrolyte membrane was investigated by determining the change in thickness, proton conductivity, and amounts of sulfonic acid groups. It was concluded that the degradation of performance in fuel cell was due to the thermal aging of the hydrocarbon polymer electrolyte membrane being exposed to the electrochemical environment with the pure oxygen acting as the oxidant gas, as well as the Nafion-based catalyst layer being subjected to high temperature for a long time, where the Pt catalyst was aggregated and sintered.

Hydrolysis of sucrose using sulfonated poly(vinyl alcohol) as catalyst

The hydrolysis of sucrose was carried out over poly(vinyl alcohol) (PVA) with sulfonic acid groups, at 80 °C. The products of sucrose hydrolysis were glucose and fructose. A series of PVA with different crosslinking degree were prepared. It was observed that the catalytic activity of PVA matrix increases with the crosslinking degree, due to the increases of the amount of sulfonic acid groups on PVA. Further, the influence of various reaction parameters, such as, catalyst loading, initial concentration of sucrose and temperature, on the hydrolysis of sucrose over PVA_40 was studied. It was found that at 80 °C, with 0.511 g of catalyst loading and with an initial concentration of sucrose of 0.6 M, a sucrose conversion of about 90%, after 3 h, could be obtained. The PVA_40 catalyst was recycled and reused with negligible loss in the activity. A simple kinetic model was developed assuming that the sucrose hydrolysis is an irreversible reaction and the first order with respect to the sucrose concentration. Since the concentration profiles of the reactant and the products do not exhibit any pronounced initial inductive period, the external and internal diffusion of the reactant and products on the catalyst were not considered. It was observed that the kinetic model fits experimental concentration data quite well.

Nanoparticles of Mesoporous SO3H‐Functionalized Si‐MCM‐41 with Superior Proton Conductivity

Nanometer-sized mesoporous silica particles of around 100-nm diameter functionalized with a large amount of sulfonic acid groups are prepared using a simple and fast in situ co-condensation procedure. A highly ordered hexagonal pore structure is established by applying a pre-hydrolysis step in a high-dilution synthesis approach, followed by adding the functionalization agent to the reaction mixture. The high-dilution approach is advantageous for the in situ functionalization since no secondary reagents for an effective particle and framework formation are needed. Structural data are determined via electron microscopy, nitrogen adsorption, and X-ray diffraction, proton conductivity values of the functionalized samples are measured via impedance spectroscopy. The obtained mesoporous SO(3)H-MCM-41 nanoparticles demonstrate superior proton conductivity than their equally loaded micrometer-sized counterparts, up to 5 x 10(-2) S cm(-1). The mesoporosity of the particles turns out to be very important for effective proton transport since non-porous silica nanoparticles exhibit worse efficient proton transport, and the obtained particle size dependence might open up a new route in rational design of highly proton conductive materials.

Tunable electrical properties of polystyrene/gold core-shell structure by in situ metallization of cationic gold complex on selective ion-exchange sites

Gold-coated polystyrene (PS) beads were fabricated by an in situ metallization route involving a cationic-gold complex with a controlled amount of sulfonic acid groups formed on the PS bead surface. The interaction ratio of SO3−to [Au(phen)Cl2]+may be estimated to be 2.4, which means that 2.4 sulfonated groups will interact with one gold cationic ligand based on geometric considerations. A modeling methodology was developed to predict the mechanical deformation, conductivity, and contact surface area of a spherical bead under compression.

Proton conducting PAMPS networks: From flexible to rigid materials

AbstractTo elaborate tailor‐made proton conducting materials showing an interesting range of flexibility, a series of conetworks combining poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS) and poly(ethylene oxide) dimethacrylate (PEGDM) with various chain lengths was synthesized. The homogeneity of these conetworks was checked by differential scanning calorimetry and dynamic mechanical thermal analysis. The swelling behavior of these materials is strongly influenced by the amount of sulfonic acid groups and the endothermal peak temperature, characteristic of the presence of bound water in the conetwork, increases from 65 to 120°C when AMPS amount increases from 10 to 75 wt %. In addition, the proton conductivity of these materials varies from 10−3 to 10−1 S cm−1, depending on the AMPS amount. The storage moduli were found to be affected by both the AMPS content in the conetwork and its crosslinking density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Pore Size Effect on Improvement of Surface Proton Conductivity for Three-Dimensionally Ordered Macroporous Silica Composite Membrane

A composite membrane composed of a three-dimensionally ordered macroporous (3DOM) silica matrix and a proton conducting polymer electrolyte was prepared. The proton conductivity of the composite membrane was successfully improved by introduction of sulfonic acid groups on the 3DOM silica surface. On decreasing pore size of the 3DOM silica matrix, a greater improvement of proton conductivity was observed. ( pore) or ( pore) improvement was attained for the composite membranes filled with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) polymer. These values are two orders of magnitude larger than those expected from the amount of sulfonic acid groups introduced on the 3DOM silica surfaces. This result suggests a formation of new proton conducting paths by an interaction between sulfonic acid groups on the 3DOM silica surface and those in the AMPS polymer electrolyte.

Acid-Catalyzed Reactions on Flexible Polycyclic Aromatic Carbon in Amorphous Carbon

Carbonization of d-glucose at 573−723 K followed by sulfonation produces a functionalized amorphous carbon material with acid catalytic activity as a solid-acid replacement for sulfuric acid. The carbon material contains phenolic hydroxyl, carboxylic acid, and sulfonic acid groups and exhibits high catalytic performance for liquid-phase acid-catalyzed reactions. Carbonization at higher temperature followed by sulfonation also results in amorphous carbon, but the resultant does not exhibit catalytic activity although the amorphous carbon has sufficient amount of sulfonic acid groups. Structural and active site analyses suggest that the marked difference in catalytic activity is due to the accessibility of reactants to sulfonic acid groups in the carbon structure.

Poly( N-isopropyl acrylamide) derivatives with pendent sulfonic acid groups and nitroxide radicals

Copolymers of N-isopropyl acrylamide, 2-acrylamido-2-methylpropane sulfonic acid and an acrylic ester of a nitroxide radical have been synthesized by radical polymerization. The products are polymers where the nitroxide side group is reversibly protonated by the sulfonic acid groups. The lower critical solution temperature ( LCST) and the amount and size of the aggregates formed in aqueous solutions above the LCST are dependent not only on the amount of sulfonic acid groups in the polymer, but also on the pH and ionic strength of the solvent. Electron paramagnetic resonance spectra of the labelled polymers are sensitive to the rate and amplitude of the segmental motion of the polymer chain, and also to the rate of proton exchange between the sulfonic acid and the nitroxide.

Quantitative analysis of sulfonic acid groups in macromolecular lignosulfonic acids and aquatic humic substances by temperature-resolved pyrolysis-mass spectrometry

A novel, selective and quantitative pyrolysis-mass spectrometric (Py-MS) procedure for sulfonic acid groups present in macromolecular lignosulfonic acids and aquatic humic substances is presented. The procedure is based on the specific Py-MS detection of sulfur dioxide, which is a characteristic pyrolysis product of sulfonic acid groups. Using this procedure, specific mass spectrometric evidence for the general occurrence of significant amounts of sulfonic acid groups in macromolecular aquatic humic substances is presented for the first time. The presence of sulfonic acid groups in aquatic humic substances fundamentally limits their isolatability on hydrophobic resin types. Several aquatichumic substance samples appear to contain sulfone structural units